On generalized wishart distributions - II: Sphericity test

Abstract

In this second part of the paper, we make use of the distribution of the trace of a generalized Wishart matrix based on elliptical models to derive the moments of statistic V used for testing sphericity for a general elliptical model. From the general expressions, we derive specific expressions for the special case of the Kotz family, which includes the Gaussian subfamily. Finally, to illustrate the usefulness of the approach, the exact distribution of the statistic V is derived in terms of the G-function by using Mellin transform and complex integration techniques.